[LPIC-1]GNU and Unix Commands 23

What does the ? symbol within regular expressions represent?

A. Match the preceding qualifier one or more times.
B. Match the preceding qualifier zero or more times.
C. Match the preceding qualifier zero or one times.
D. Match a literal ? character.

題解

「?」在正規表示式中代表符號出現0次或1次。所以答案是選項C。